Carbohydrates form an important ingredient of various nutrition. They can generally be distinguished in fast (release) carbohydrates, slow (release) carbohydrates and resistant carbohydrates. The fast and slow carbohydrates are digestible carbohydrates, i.e they are digested in the stomach/small intestines. To these categories belong mainly starch and their derivates, e.g. hydrolysates and sugars.
The glycaemic index (GI) is a measure of the effects of carbohydrates on blood sugar levels. The slow digestible carbohydrates provide a lower glycaemic index than the fast digestible carbohydrate. A lower glycaemic index is an indication for slower rates of digestion and absorption of the foods' carbohydrates and may also indicate greater extraction from the liver and periphery of the products of carbohydrate digestion. A lower glycaemic response usually equates to a lower insulin demand but not always, and may improve long-term blood glucose control and blood lipids. The insulin index is also useful for providing a direct measure of the insulin response to a food.
Resistant carbohydrate is not digested in the small intestine. Resistant carbohydrates contribute to the total dietary fibre. Examples of resistant carbohydrates are, resistant starches (Type I to III), fructooligosaccharides, galactooligosaccharides and polydextrose. Some of these can be fermented by microflora in the colon, such as fructoologosacharides and galactoologosaccharides. Resistant carbohydrates that provide nutrition to the microflora may contribute to specific changes in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-being and/or health. These are commonly referred to as prebiotics. Examples of prebiotics are fructooligosaccharides and galactooligosaccharides.
Research over the last decades, pointed out a relationship between dietary fibre and the prevention of certain diseases, for example the prevention of diabetes type II. Different prebiotic carbohydrates have different effects on the microflora and/or may offer different health benefits. For example, prebiotics that are fermented relatively quickly may mainly provide nourishment to bacteria in the proximal part of the colon, whereas prebiotics that are fermented relatively quickly may mainly provide nourishment to bacteria in the distal part of the colon. Thus, be selecting a type of prebiotic it may be possible to selectively target microflora in a specific part of the colon. Also different prebiotics may give rise to the formation of different break-down products (different organic acids).
Various technologies have been described relating to the preparation of polysaccharides with potential dietary benefits.
U.S. Pat. No. 6,559,302 relates to a method to prepare an edible polysaccharide wherein a glucose source is reacted with another polyol, such as sorbitol in the presence of a mineral acid. It is not mentioned to use at least two different carbohydrates as a starting material, wherein one is a glucose source selected from glucose, maltose and polydextrose with a polysaccharide (different from said glucose source)—which polysaccharide is a glucan. It is apparent that the used starting materials are all relatively small molecules (dextrose and sorbitol) and there is no suggestion that it would be possible to prepare a branched glucan by polycondensation using a polysaccharide, let alone a polysaccharide that has a polymerisation degree high enough to make it pregelatinisable, or a polysaccharide with a high degree of polymerisation whereby it is not meltable in pure form, due to decomposition at a temperature below its (hypothetical) melting point.
EP 2 151 500 A1 relates to an enzymatic method for the preparation of a branched glucan with water soluble fibre properties with a significantly low-digestibility and effects of inhibiting the elevation of blood sugar level. According to the description, the enzymatically prepared glucan is different from glucans formed in a chemical reaction making use of glucose that is polymerised. In particular, the glucan is characterised by a specific methylation analysis. It is further mentioned that the glucan is hardly digestible by salivary alpha amylase or alpha amylase from pancreas or small intestines, and does not induce acid fermentation in the mouth.
When formulated in a nutritional composition, carbohydrates, in particular fibres and digestible polysaccharides, may also affect other properties of the composition, such as organoleptic effects (e.g. mouth-feel, texture), of the composition, or rheological properties of the composition, such as viscosity. In particular, there is a need for carbohydrates with a relatively low caloric value that have a desirable organoleptic effect, such as a fat-mimicking effect.
Thus, there is a continuing interest for novel digestible and for novel indigestible carbohydrates, which may be used to formulate nutritional compositions or be used for preparing food supplements or pharmaceutical compositions.